Activity sensor for pacemaker control

Abstract

A cardiac pacer is provided which incorporates a sensor responsive to the physical activity of the pacer-wearing patient. The output of the physical activity sensor is utilized by control circuitry of a physiological sensor to enable the physiological sensor to monitor a selected physiological parameter only if the physical activity of the pacer-wearing patient exceeds a selected threshold. In this manner, the electrical energy requirements of the pacer are lessened.

What is claimed is: 
     
       1. A cardiac pacing system which comprises: an implantable pacer;   passive means requiring no power for sensing the physical activity of the pacer-wearing patient;   a physical activity threshold detector coupled to said physical activity sensing means;   means for sensing a selected physiological parameter of the patient; and   means for controlling the operation of said physiological parameter sensing means in response to detection of a physical activity threshold by said physical activity threshold detector.   
     
     
       2. A cardiac pacing system as described in claim 1, said implantable pacer including a sense amplifier for receiving sensed cardiac signals and pulse rate and timing means. 
     
     
       3. A cardiac pacing system as described in claim 1, including signal conditioning means coupling said passive member to said physical activity threshold detector. 
     
     
       4. A cardiac pacing system as described in claim 3, including means for programming said physical threshold detector for operational control at a selected threshold of physical activity. 
     
     
       5. A cardiac pacing system as described in claim 1, said controlling means including means for powering said physiological parameter sensing means; said controlling means being operable to enable said powering means only if a selected physical activity threshold is detected by said physical activity threshold detector. 
     
     
       6. A cardiac pacing system as described in claim 1, said physical activity sensing means comprising a piezoelectric element that is passive whereby no power is required to render it operational, said piezoelectric element being operative to generate a signal responsive to physical activity of the pacer-wearing patient. 
     
     
       7. A cardiac pacing system as described in claim 1, said physiological parameter sensing means being adapted to sense a physiological parameter from one or more of the group consisting of the partial pressure of oxygen (pO 2 ), blood pressure, core temperature, CO 2  and pCO 2 , O 2  in addition to pO 2 , pH, respiration rate, respiration depth, and ventricular volume. 
     
     
       8. A cardiac pacing system as described in claim 7, said physical activity sensing means comprising a piezoelectric element that is passive whereby no power is required to render is operational, said piezoelectric element being operative to generate a signal responsive to physical activity of the pacer-wearing patient. 
     
     
       9. A cardiac pacing system which comprises: an implantable pacer;   said implantable pacer including a sense amplifier for receiving sensed cardiac signals and pulse rate and timing means;   means for sensing the physical activity of the pacer-wearing patient, said physical activity sensing means comprising a passive member requiring no power carried by the implantable pacer;   a physical activity threshold detector;   signal conditioning means coupling said passive member to said physical activity threshold detector;   means for programming said physical activity threshold detector for operational control at a selected threshold of physical activity;   means for sensing a selected physiological parameter of the patient, said physiological parameter sensing means being adapted to sense a physiological parameter from one or more of the group consisting of the partial pressure of oxygen (pO 2 ), blood pressure, core temperature, CO 2  and pCO 2 , O 2  in addition to pO 2 , pH, respiration rate, respiration depth, and ventricular volume; and   means for controlling the operation of said physiological parameter sensing means in response to detection of a physical activity threshold by said physical activity threshold detector, said controlling means including means for powering said physiological parameter sensing means and being operable to enable said powering means only if a selected physical activity threshold is detected by said physical activity threshold detector.   
     
     
       10. A cardiac pacing system as described in claim 9, said physical activity sensing means comprising a piezoelectric element that is passive whereby no power is required to render it operational, said piezoelectric element being operative to generate a signal responsive to physical activity of the pacer-wearing patient. 
     
     
       11. A cardiac pacing system which comprises: an implantable pacer;   means for sensing cardiac activity and for transmitting cardiac activity signals to the pacer;   means for stimulating cardiac muscle;   said pacer including pulse generating means located inside the pacer for providing stimulating pulses to the stimulating means;   passive means requiring no power for sensing the physical activity of the pacer-wearing patient;   means for sensing a selected physiological parameter of the pacer-wearing patient;   a physical activity threshold detector, coupled to said physical activity sensing means;   means for powering said physiological parameter sensing means;   means for inhibiting power to said physiological parameter sensing means unless said physical activity threshold detector detects at least a predetermined threshold of physical activity; and   means for controlling the pulse generating means to vary the stimulating pulse output therefrom in response to the sensed physiological parameter.   
     
     
       12. A cardiac pacing system as described in claim 11, wherein said means for sensing cardiac activity, means for stimulating cardiac muscle and means for sensing a selected physiological parameter all comprise a single, unitary lead connected to the pacer. 
     
     
       13. A cardiac pacing system as described in claim 11, said physical activity sensing means comprising a piezoeletric element that is passive whereby no power is required to render it operational, said piezoelectric element being operative to generate a signal responsive to physical activity of the pacer-wearing patient. 
     
     
       14. A cardiac pacing system as described in claim 11, said physiological parameter sensing means being adapted to sense a physiological parameter from one or more of the group consisting of the partial pressure of oxygen (pO 2 ), blood pressure, core temperature, CO 2  and pCO 2 , O 2  in addition to pO 2 , pH, respiration rate, respiration depth, and ventricular volume. 
     
     
       15. A cardiac pacing system which comprises: an implantable pacer;   means for sensing cardiac activity and for transmitting cardiac activity signals to the pacer;   means for stimulating cardiac muscle;   said pacer including pulse generating means located inside the pacer for providing stimulating pulses to the stimulating means;   means for sensing the physical activity of the pacer-wearing patient, said physical activity sensing means comprising a piezoelectric element that is carried by the implantable pacer and is passive whereby no power is required to render it operational, said piezoelectric element being operative to generate a signal responsive to physical activity of the pacer-wearing patient;   means for sensing a selected physiological parameter of the pacer-wearing patient, said physiological parameter sensing means being adapted to sense a physiological parameter from one or more of the group consisting of the partial pressure of oxygen (pO 2 ), blood pressure, core temperature, CO 2  and pCO 2 , O 2  in addition to pO 2 , pH respiration rate, respiration depth, and ventricular volume;   a physical activity threshold detector;   a signal conditioning means coupling said piezoelectric element to said physical activity threshold detector;   means for powering said physiological parameter sensing means;   means for inhibiting power to said physiological parameter sensing means unless said physical activity threshold detector detects at least a predetermined threshold of physical activity; and   means for controlling the pulse generating means to vary the stimulating pulse output therefrom in response to the sensed physiological parameter.   
     
     
       16. A physiological sensitive cardiac pacing process which comprises the steps of: providing an implantable pacer;   sensing the physical activity of the pacer-wearing patient by a passive element requiring no power;   sensing a selected physiological parameter of the patient;   detecting a selected threshold of the patient's physical activity; and   controlling the physiological sensing in response to detection of the selected physical activity threshold.   
     
     
       17. A physiological sensitive cardiac pacing process as described in claim 16, wherein the step of sensing the selected physiological parameter includes the steps of sensing a physiological parameter from one or more of the group consisting of the partial pressure of oxygen (pO 2 ), blood pressure, core temperature, CO 2  and pCO 2 , O 2  in addition to pO 2 , pH, respiration rate, respiration depth, and ventricular volume. 
     
     
       18. A physiological sensitive cardiac pacing process which comprises the steps of: providing an implantable pacer;   sensing cardiac activity and transmitting cardiac activity signals to the implantable pacer;   providing stimulating pulses for stimulating the cardiac muscle;   sensing the physical activity of the pacer-wearing patient by a passive element requiring no power;   sensing a selected physiological parameter of the pacer-wearing patient; and   inhibiting power to said means for sensing the physiological parameter unless the physical activity that is sensed is at least a predetermined physical activity threshold.